Heathrow Airport has warned that its planned third runway may not open until 2039, four years later than the British government’s target. The airport still aims to secure planning approval by 2029, but now says construction could take up to a decade after approval, according to Reuters. The revised timetable exposes the financing, regulatory and environmental risks surrounding one of Europe’s largest proposed infrastructure projects.

A target slips

Airport executives have told ministers that the original goal of opening the runway in 2035 is no longer achievable, Sky News reported Saturday. Heathrow’s public position is more conditional: it hopes to obtain a development consent order by 2029 and bring the runway into service within 10 years.

The distinction matters for investors and policymakers. A 2039 opening would extend the period before the new capacity generates landing fees, retail revenue and cargo growth. It would also increase exposure to construction inflation, borrowing costs, political turnover and changes in travel demand across the global aviation market. Heathrow has not said the expansion is canceled, but a longer delivery schedule makes every underlying assumption more consequential.

A major private investment

The wider expansion has been estimated at roughly £49 billion, including the runway, terminal works and major changes to roads and utilities. Heathrow says the project would increase capacity, lower fares through more competition and strengthen Britain’s international links. On its expansion site, the airport describes itself as the United Kingdom’s largest port by value, supporting about £200 billion in annual trade and 80,000 jobs at the airport.

Those projected benefits depend on completing a complex package of enabling works. Plans include changes around the M25 motorway, new surface-access infrastructure and relocation or redesign of existing facilities. Each element requires coordination among regulators, local authorities, utilities and contractors before the runway itself can operate.

Government still backs expansion

The British government has treated Heathrow expansion as a central economic-growth project. In June, the Department for Transport launched a planning consultation and said a third runway could support more than 60,000 local jobs and deliver as much as £42 billion in national benefits. The government also kept its goal of reaching a final planning decision in 2029.

The draft policy does not itself grant permission to build. It sets the framework against which a future development-consent application will be judged, including tests on noise, air quality, climate effects and economic growth. The official consultation closed on Sept. 1, leaving ministers to decide how the final policy will balance those conditions.

Environmental obligations loom

Britain’s Climate Change Committee has warned that airport expansion is incompatible with current policies for reaching net-zero emissions by 2050. The independent adviser said the government would need to require airlines to address all aviation emissions, including through sustainable aviation fuel and engineered carbon removals. Sustainable fuel still accounts for less than 1% of global jet-fuel use and costs several times more than conventional fuel, Reuters reported.

A delayed opening could provide more time for cleaner technologies to scale, but it could also postpone the economic case used to justify the project. Heathrow says growth and net-zero goals can be achieved together. The government’s draft framework requires any proposal to comply with legal climate and air-quality limits, making environmental performance a commercial issue as well as a planning condition.

Local opposition remains

Communities around the airport have opposed a third runway for years because of aircraft noise, air pollution, road congestion and the loss of homes. Richmond Council, one of the local authorities challenging expansion, says the draft policy gives too much weight to growth and too little protection to residents. Its position statement notes that expansion could add about 260,000 flights a year.

Longer timelines can intensify that conflict. Residents and businesses face a prolonged period of uncertainty over property, transport routes and flight paths, while Heathrow must keep planning teams and supply-chain partners engaged before construction revenue begins. Any legal challenge could add further delay, even if the government maintains political support.

What comes next

The immediate milestone is the government’s response to its policy consultation, followed by Heathrow’s formal planning application. The airport must show that its proposal is financeable, buildable and compliant with environmental rules. Regulators will also determine how costs may be recovered and what portion, if any, can flow through airport charges paid by airlines.

The shift toward 2039 does not end the third-runway effort, but it changes the business calculation. Supporters will argue that more capacity remains essential for trade and connectivity. Critics will point to cost escalation, climate obligations and competing infrastructure needs. For investors, airlines and contractors, the central question is no longer only whether Britain will expand Heathrow, but whether the project can survive another decade of policy, financing and technology risk before the first flight takes off.